1. Field of the Invention
The present invention generally relates to ultraviolet-light irradiation apparatuses and, more particularly, to an ultraviolet-light irradiation apparatus for eliminating an electric charge after various plasma processes in a semiconductor manufacturing process.
In a manufacturing process of a flash memory, irradiation of an ultraviolet-light by a low-pressure mercury lamp is widely used in a process of eliminating an electric charge after carrying out a plasma process such as an etching process. That is, an electric charge of a semiconductor wafer is eliminated by irradiating an ultraviolet light onto the semiconductor wafer. The low-pressure mercury lamp used for such a process is a consumable component part, and it is required to replace the low-pressure mercury lamp with new one since an illumination intensity will become below a specified value when certain hours of use has passed. Therefore, there is a demand for reducing a cost for replacing a low-pressure mercury lamp. Moreover, the is a demand for improving productivity by improving an irradiation efficiency of a low-pressure mercury lamp so as to reduce an irradiation time.
2. Description of the Related Art
FIG. 1 is an illustrative cross-sectional view of a conventional ultraviolet-light irradiation apparatus 1 used for eliminating an electric charge of semiconductor wafers. FIG. 2 is a side view of the ultraviolet-light irradiation apparatus 1 shown in FIG. 1. The ultraviolet-light irradiation apparatus 1 comprises a wafer support plate 2 as a placement stage provided in a housing and a plurality of low-pressure mercury lamps 4 provided above the wafer support plate 2. The low-pressure mercury lamp 4 emits an ultraviolet light having a wave length of 254 nm, and irradiates the ultraviolet light onto a wafer W placed on the wafer support plate 2.
An electric charge of the wafer W is eliminated by the irradiation of the ultraviolet light. A reflective mirror 3 is provided above the low-pressure mercury lamps 4. The reflective mirror 3 reflects the ultraviolet light, which is emitted upward by the low-pressure mercury lamps 4, so that the ultraviolet light is irradiated onto the wafer W as much as possible. Moreover, a reflective mirror 5 is also provided on each side of the low-pressure mercury lamps 4.
FIG. 3 is a plan view of the reflective mirror 3 viewed from the reflective surface side. The reflective mirror 3 is formed as a bottom surface of an exhaust passage 7, and is provided with may exhaust holes 3a, which are small holes or openings, as shown in FIG. 3. An end (right-hand side of FIG. 2) of the exhaust passage 7, which has the reflective mirror 3 as a bottom surface, is closed, and air is suctioned through the other end (left-hand side of FIG. 2) of the exhaust passage 7. Therefore, air heated by a temperature rise of the tube walls of the low-pressure mercury lamps 4 is suctioned into the exhaust passage 7 through the exhaust holes 3a, and is exhausted to an exterior of the ultraviolet-light irradiation apparatus 1.
Accordingly, the hot air around the low-pressure mercury lamps 4 is exhausted so that the temperature of the tube walls of the low-pressure mercury lamps 4 is prevented from rising excessively. Moreover, a water-cooling mechanism 9 is provided above the exhaust passage 7 so as to cool the ultraviolet-light irradiation apparatus 1 including the low-pressure mercury lamps 4, which also prevents an excessive temperature rise.
The exhaust holes 3a shown in FIG. 3 are circular pores having a diameter of 10 mm, and are arranged along a longitudinal direction of the low-pressure mercury lamps 4. As mentioned above, since air is suctioned through one end of the exhaust passage 7 and exhausted from the other end, a pressure difference is generated between the opposite ends of the exhaust passage 7, which causes deviation in an amount of air suctioned through the exhaust holes 3a. 
That is, an amount of air suctioned through the exhaust holes 3a near the suction side (left-hand side of FIG. 2) is larger than an amount of air suctioned through the exhaust holes 3a near the opposite side (right-hand side of FIG. 2). If an amount of exhaust air passing through the exhaust passage 7 is adjusted so as to set a temperature of the low-pressure mercury lamps 4 at the side opposite to the suction side to an appropriate temperature, the low-pressure mercury lamps 4 near the suction side are excessively cooled, which prevents the whole low-pressure mercury lamps 4 from being uniformly cooled.
Thus, there is a problem in that an excessively cooled potion is formed in the tube walls of the low-pressure mercury lamp 4, which reduces the irradiation efficiency. Moreover, the reflective surface of the reflective mirror 3 shown in FIG. 3 has mere a flat surface configuration, and the reflective efficiency is not taken into consideration. That is, as indicated by an arrow in FIG. 1, an ultraviolet light projected from an upper part of the low-pressure ultraviolet light 4 is reflected in a direction other than a direction toward the wafer W or irradiated onto a side of the apparatus without reflection. Thus, the consideration for turning an ultraviolet light in the direction of wafer W efficiently is not made with respect to the reflective mirror 3 which has the reflective surface of a mere flat-surface configuration, and there is a problem in that efficient ultraviolet-light irradiation is not performed.
It is a general object of the present invention to provide an improved and useful ultraviolet-light irradiation apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide an ultraviolet-light irradiation apparatus in which irradiation lamps are uniformly cooled to achieve an appropriate temperature of the walls of the lamps and the ultraviolet light emitted from the lamps is efficiently reflected toward an object to be irradiated so that the ultraviolet light is efficiently irradiated onto the object to be irradiated.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention an ultraviolet-light irradiation apparatus comprising: a plurality of low-pressure mercury lamps arranged in parallel; a placement stage provided under the low-pressure mercury lamps so that an object onto which an ultraviolet light emitted by the low-pressure mercury lamps is irradiated is placed on the placement stage; a reflective mirror arranged above the low-pressure mercury lamps so as to reflect the ultraviolet light emitted by the low-pressure mercury lamps; and an exhaust passage defined by the reflective mirror, the exhaust passage suctioning air around the low-pressure mercury lamps and exhausting the suctioned air to outside, wherein the reflective mirror has a plurality of openings arranged along a longitudinal direction of the low-pressure mercury lamps, and a part of the openings has a size different from a size of other parts of the openings.
According to the above-mentioned invention, an amount of air suctioned through the reflective mirror can be locally changed along the longitudinal direction of the low-pressure mercury lamps so as to adjust a degree of cooling partially. Therefore, when variation arises in a cooling effect along the longitudinal direction of the low-pressure mercury lamps, a uniform cooling effect can be acquired by locally changing a size of a part of the openings. Thus, a bulb temperature of the low-pressure mercury lamps can be uniformized, which extends the service life of the low-pressure mercury lamps.
In the ultraviolet-light irradiation apparatus according to the present invention, the exhaust passage may have a closed end and a suction end opposite to the closed end along a longitudinal direction thereof so as to suction air through the opening by exhausting the air from the suction end, and the size of the openings may gradually increase from the suction end toward the closed end of the exhaust passage.
The reflective mirror may be divided into a plurality of areas along the longitudinal direction of the low-pressure mercury lamps, and the openings located in one of the adjacent areas closer to the closed end of the exhaust passage may be larger than the other area closer to the suction end of the exhaust passage. An interval of the openings may locally differ along the longitudinal direction of the low-pressure mercury lamps.
Additionally, there is provided according to another aspect of the present invention an ultraviolet-light irradiation apparatus comprising: a plurality of low-pressure mercury lamps arranged in parallel; a placement stage provided under the low-pressure mercury lamps so that an object onto which an ultraviolet light emitted by the low-pressure mercury lamps is irradiated is placed on the placement stage; a reflective mirror arranged above the low-pressure mercury lamps so as to reflect the ultraviolet light emitted by the low-pressure mercury lamps; and an exhaust passage defined by the reflective mirror, the exhaust passage suctioning air around the low-pressure mercury lamps and exhausting the suctioned air to outside, wherein the reflective mirror has a plurality of openings having the same size and arranged along a longitudinal direction of the low-pressure mercury lamps, and an interval of the openings locally differs along the longitudinal direction of the low-pressure mercury lamps.
According to the above-mentioned invention, a density of openings can be locally changed by locally changing the interval of the openings, thereby locally changing an amount of air suctioned through the reflective mirror. Therefore, a bulb temperature can be adjusted along the longitudinal direction of the low-pressure mercury lamps. Thus, when variation occurs in the cooling effect along the longitudinal direction of the low-pressure mercury lamps, a uniform cooling effect can be acquired by locally changing the interval of the openings of the reflective mirror. Thereby, the bulb temperature of the low-pressure mercury lamps can be unifromized, which results in improvement of the service life of the low-pressure mercury lamps.
Additionally, there is provided according to another aspect of the present invention an ultraviolet-light irradiation apparatus comprising: a plurality of low-pressure mercury lamps arranged in parallel; a placement stage provided under the low-pressure mercury lamps so that an object onto which an ultraviolet light emitted by the low-pressure mercury lamps is irradiated is placed on the placement stage; and a reflective mirror arranged above the low-pressure mercury lamps so as to reflect the ultraviolet light emitted by the low-pressure mercury lamps, wherein the reflective mirror has a protruding reflective part protruding into a space between the adjacent low-pressure mercury lamps.
According to the above-mentioned invention, the ultraviolet light emitted by the low-pressure mercury lamps can be efficiently reflected toward the object to be irradiated by the protruding reflective part. Thus, the illuminance of the ultraviolet-light on the object to be irradiated in the area between the adjacent low-pressure mercury lamps can be increased as compared with a reflective mirror, which does not have a projection reflective part. Thereby, the illuminance of the ultraviolet light on the object to be irradiated is uniformaized over the entire surface of the object, and a high-quality process can be performed on the object to be irradiated.
In the ultraviolet-light irradiation apparatus according to the above-mentioned invention, the protruding reflective part of the reflective mirror may have an outer configuration defined by two sides of a triangle having a top located in the middle between the adjacent low-pressure mercury lamps. The reflective mirror may be made of a metal plate, and the protruding reflective part is formed by bending the metal plate.
The ultraviolet-light irradiation apparatus may further comprise an exhaust passage defined by the reflective mirror, the exhaust passage suctioning air around the low-pressure mercury lamps and exhausting the suctioned air to outside, wherein the reflective mirror may have a plurality of openings having the same size and arranged along a longitudinal direction of the low-pressure mercury lamps, and the exhaust passage may have a closed end and a suction end opposite to the closed end along a longitudinal direction thereof so as to suction air through the opening by exhausting the air from the suction end, the size of the openings gradually increasing from the suction end toward the closed end of the exhaust passage.
The reflective mirror may be divided into a plurality of areas along the longitudinal direction of the low-pressure mercury lamps, and the openings located in one of the adjacent areas closer to the closed end of the exhaust passage may be larger than the other area closer to the suction end of the exhaust passage.
The ultraviolet-light irradiation apparatus according to the present invention may be configured and arranged to irradiate the ultraviolet light onto the object to be irradiated so as to cure a resist applied to the object to be irradiated. Or, the ultraviolet-light irradiation apparatus may be configured and arranged to irradiate the ultraviolet light onto the object to be irradiated so as to carry out optical cleaning of an organic matter on the object to be irradiated.
Additionally, there is provided according to another aspect of the present invention a resist curing method comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a reflective mirror located above the low-pressure mercury lamps so as to cure a resist on the object to be irradiated; and suctioning air around the low-pressure mercury lamps into an exhaust passage defined by the reflective mirror and exhausting the suctioned air to outside, the air being suctioned through a plurality of openings formed in the reflective mirror and arranged along a longitudinal direction of the low-pressure mercury lamps, a part of the openings having a size different from a size of other parts of the openings.
Additionally, there is provided according to another aspect of the present invention a resist curing method comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a reflective mirror located above the low-pressure mercury lamps so as to cure a resist on the object to be irradiated; suctioning air around the low-pressure mercury lamps into an exhaust passage defined by the reflective mirror and exhausting the suctioned air to outside, the air being suctioned through a plurality of openings having the same size and formed in the reflective mirror and arranged along a longitudinal direction of the low-pressure mercury lamps, an interval of the openings locally differing along the longitudinal direction of the low-pressure mercury lamps.
Additionally, there is provided according to another aspect of the present invention a resist curing method, comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; and reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a protruding reflective part of a reflective mirror so as to cure a resist on the object to be irradiated, the protruding reflective part protruding into a space between the adjacent low-pressure mercury lamps.
Additionally, there is provided according to another aspect of the present invention an optical cleaning method of an organic matter, comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a reflective mirror located above the low-pressure mercury lamps so as to optically remove the organic matter on the object to be irradiated; and suctioning air around the low-pressure mercury lamps into an exhaust passage defined by the reflective mirror and exhausting the suctioned air to outside, the air being suctioned through a plurality of openings formed in the reflective mirror and arranged along a longitudinal direction of the low-pressure mercury lamps, a part of the openings having a size different from a size of other parts of the openings.
Additionally, there is provided according to another aspect of the present invention an optical cleaning method of an organic matter, comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a reflective mirror located above the low-pressure mercury lamps so as to optically remove the organic matter on the object to be irradiated; and suctioning air around the low-pressure mercury lamps into an exhaust passage defined by the reflective mirror and exhausting the suctioned air to outside, the air being suctioned through a plurality of openings having the same size and formed in the reflective mirror and arranged along a longitudinal direction of the low-pressure mercury lamps, an interval of the openings locally differing along the longitudinal direction of the low-pressure mercury lamps.
Further, there is provided according to another aspect of the present invention an optical cleaning method of an organic matter, comprising: generating an ultraviolet light by a plurality of low-pressure mercury lamps arranged in parallel; and reflecting the ultraviolet light emitted by the low-pressure mercury lamps toward an object placed on a placement stage by a protruding reflective part of a reflective mirror so as to optically remove the organic matter on the object to be irradiated, the protruding reflective part protruding into a space between the adjacent low-pressure mercury lamps.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with accompanying drawings.